[libvirt-users] libvirtd via unix socket using system uri

[Peter Crowther]

On Tue, 30 Apr 2019 at 10:48, Daniel P. Berrangé <berrange at redhat.com>
wrote:

> On Tue, Apr 30, 2019 at 10:45:03AM +0100, Peter Crowther wrote:
> > On Tue, 30 Apr 2019 at 10:40, Michal Privoznik <mprivozn at redhat.com>
> wrote:
> >
> > > Is there any problem running libvirtd as root?
> > >
> > > Yes, in the regulated environment in which I work!  I have to do far
> more
> > thorough threat analysis than I would do if I knew which capabilities it
> > had.  So far, we've accepted the extra work; but it would be wonderful to
> > be able to run a locked-down virtualisation environment.
>
> Libvirtd system mode will want cap_net_admin in order to setup TAP devices
> and cap_sys_admin to manage disk permissions to grant QEMU access, at which
> point you've lost any security benefit of running it unprivileged with
> selective capabilities.
>
> Would it fail hard without these, even if using (for example) pre-created
Ceph block storage, which is our use case?  Or would it only fail when it
tried to make use of a capability that wasn't present?  My reading of
capabilities is that behaviour is indistinguishable until you get an EPERM?

I agree that CAP_DAC_OVERRIDE (per your later mail) is game over for any
system, as that allows write of any config file.  It'd be lovely to find a
way of not requiring that.  Knowing that a piece of software can't
maliciously insert kernel modules, can't write or clear audit trails, and
can't do raw I/O already considerably reduces the analysis.

- Peter
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